How much power do I need?
The answer may surprise you but, it all comes down to some basic electrical calculations. The way wattage is determined—using what’s known as the “indirect method”—is a simple equation: volts x amps = power (watts).
The only secret you need to know is that watts are measured in watt hours. That is to say, one kilowatt-hour is the amount of wattage used over the time period of one hour (1,000 watts/hour).
I have always carried with me a portable jump starter. It has 900 amps always available and can deliver 2000+ amps for a short period of time (peak power). I once started 20 cars in a parking lot during ice cold weather before it died!
Let’s do the math.
Every device that uses electricity, from a night light to your cell phone charger to a stadium transformer, has a label that rates its power (wattage) consumption and output. Consider my 900 amp jumper: operating at 12 volts, I’ve got 10,800 watts (or almost 11 kilowatts) available from this little box (900 x 12 = 10,800)! By any measure, that’s a lot of power to use.
But, I’m going to convert that power into 110 volts AC so, we take those 1.8 KW and divide it by 110. The converted amps I’ll get, give or take a little for the efficiency factor of the converter, is just over 98 amps. Still enough to kill ya under the right circumstances!
My laptop charger uses 1.5 amps and my cell phone charger uses about a half an amp. That’s 2 amps. If I were to drain the jumper all the way to dead, I could charge both my laptop and my cell phone, continuously, for forty nine hours!
With 8 hours of sleep each night, my devices can charge for more than six days from one jumper charge. And the jumper takes only a day to be fully recharged when plugged into the converter with the engine running.
That also means I can use my flat panel television every night using only 35 watts—without killing my car battery! I’ve set up the converter to turn on whenever I start up the Sienna so, I’ll have a nice cycle of charging the jumper while driving and plenty of battery power when the engine is off —running my AC devices from the jumper.
Powerful knowledge, this “indirect method!”
Drive safe and take care.